Various polymer and resin mixtures have been proposed for adhesives with strong bonding properties for various substrates and these have been successful to varying degrees. However, the blends of this invention have remarkably superior properties when used as adhesives. Thus the object of this invention is to provide modified polyolefin resins with improved adhesion to substrates such as polar polymers, metals, glass, paper, wood, etc. These resins can be applied in any conventional manner and typical application processes are lamination, extrusion coating, coextrusion, powder coating, blow molding, etc.
It is well known that laminates of polyolefins with dissimilar substrates have many desirable characteristics. However, it is often difficult to adhere polyolefins to dissimilar substrates because of differences in physical and chemical structure. To overcome bonding difficulties, either an adhesive layer is required between the polyolefin and the substrates or the conventional polyolefin is replaced by a more expensive highly polar copolymer of the polyolefin such as an ionomer resin. Although the ionomer resin may show good adhesion, the bond formed is easily weakened by exposure to moisture or common solvents.
Another method for improving adhesion is to treat the surface of the polyolefin by corona. The bond so formed initially results in improved adhesion to polar substrates but is weakened by exposure to moisture.
Still another method for improving adhesion is to graft polar functional groups onto the polyolefin backbone chain. The most common graft copolymers are acrylic acid or maleic anhydride grafted onto polypropylene or polyethylene as described or referenced in U.S. Pat. Nos. 3,658,948; 3,856,889 and 3,868,433. These graft copolymers when applied as in this invention do not give the adhesive power of the products of this invention.